The complexity of the human brain presents a challenge to scientists striving for an understanding of the molecular basis of neuronal development and function. Nevertheless, advances in genome technologies have led to the identification of several genes, mutated in neurological disorders that are important for brain development and function. Furthermore, the ability to disrupt genes in the mouse germline provides an opportunity to develop models and to test the contributions of specific genes to neurobiological processes. The information obtained from these studies is relevant to human diseases because cellular and molecular mechanisms are largely conserved between mice and humans.